Unlike other tissues in the body, spinal discs have a low blood supply and are therefore unable to repair themselves. As humans age, the discs in the back and neck start to deteriorate. The name for this condition, degenerative disc disease, is a misnomer because this issue is not a disease but rather a common way of describing the structural changes that naturally occur in the spine. For this reason, some medical professionals consider degenerative disc disease a controversial diagnosis.
When a person sits down, the load on the discs in the lower back increases as much as three times than while standing. Normally, the discs in the back have a soft, jellylike layer called the nucleus pulposus on the inside; a firmer fibrous tissue structure on the outside, the annulus fibrosus, acts as a cushion. If the outer layer tears, the inner layer is forced out through the tear. In such cases, the increased load from sitting causes both pressure and pain. Walking, running, stretching, or lying down eases the discomfort for some individuals.
In a healthy back, the discs between the vertebrae provide height, which allows an individual to move and bend. The discs take on the mechanical stress of everyday movements, absorbing pressure and keeping the spine flexible. As the disc tissue deteriorates, it no longer provides the cushioning protection between the vertebrae. Without the cushion, there is reduced flexibility. An individual with degenerative disc disease may notice pain when they bend over, reach for something on a shelf, or perform any twisting motion.
People with degenerative disc disease may experience sciatica, a pain that starts in the lower back or buttocks, then travels down one or both legs to the foot or calf. The spinal cord does not run through the entire lower back. Instead, horse-tail-shaped nerve roots come off the spinal cord at the upper part of the lumbar spine. If a degenerated disc collides with the nerve root in the lower back, it may irritate or compress the sciatic nerve, leading to pain that radiates away from the origin.
Physicians describe numbness as an inability to feel something touching the skin, while tingling is a pins-and-needle sensation. Pressure on a nerve causes numbness and can cause a pins-and-needles sensation as well. Degenerative disc changes that affect the nerves in the neck exert pressure on the spinal cord and cause tingling, aching, or numbness in the arm or hand. A tingling sensation may indicate pressure on specific nerves, nerve inflammation, nerve irritation, or pinched nerves. People who have sciatica often report a tingling sensation in their legs as well.
As discs become less supple, they also narrow. Their ability to provide adequate cushioning for the vertebrae declines, and the vertebrae start to shift. This movement affects other nearby bones and may lead to pinched nerves and muscle spasms. Osteoarthritis often accompanies degenerative disc disease. It puts pressure on the spinal cord, which can lead to spasms. Herniated or bulging discs exert pressure on nerves and result in muscle spasms, as well.
Those with degenerative disc disease experience pain that is directly related to the location of the affected disc. If the disc is in the neck area, the individual will most likely feel pain in the neck, possibly beginning as stiffness, that radiates into the shoulder, arm, and hand. As the cervical discs lose fluid, they dry out and become less flexible. The distance between the vertebrae decreases and interferes with the normal range of motion. Simple movements, such as turning the head, may become painful.
Sometimes an injury such as a fall can lead to a herniated disc, which may trigger degenerative disc disease. An injured individual with a healthy back may feel some pain following the accident, but the damage eventually heals. The person with disc degeneration not only experiences trauma from the injury, but also excessive swelling and additional degeneration symptoms. The injury is much more likely to damage the cartilage on the facet side of the vertebrae, which creates an extra burden on the disc. Years after the injury, these individuals are more likely to develop osteoarthritis or bone spurs.
A degenerative back condition can lead to painful dysfunction in the legs. Damage to the nerve root may cause not only muscle weakness in the hips and legs but foot drop as well. Foot drop is the inability to lift the front part of the foot off the floor. Radiating or burning pain and sensory loss may accompany the muscle weakness. If nerve root damage is the result of nerve compression, the individual may also exhibit a loss of reflexes. Compression can lead to the death of nerve cells, which may require surgical intervention.
Pain from degenerative disc disease may last for a few days or continue for months. Sometimes the pain is low and constant, or it may become severe and disabling. Although the condition can occur in any part of the back, the neck and lower back are the most common sites. Any movement, including coughing, sneezing, or standing for long periods, could lead to pain that spreads from the back to the buttocks and upper thighs. The condition starts with disc damage, but it soon affects the entire spine.
People with degenerative disc disease often describe the sensation that their neck or back is "giving out" and unable to provide the necessary support. Physicians say this is due to spinal instability resulting from spinal disc degeneration. As the disc loses height, friction builds between the vertebrae. Pain, in addition to a feeling that the neck or back is "locking up" is common. The person may have difficulty getting up from a chair or straightening their spine.
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